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Order Batch Formations for Less Picker Blocking in a Narrow-Aisle Picking System
Hong, Soondo Korean Institute of Industrial Engineers 2015 Industrial Engineeering & Management Systems Vol.14 No.3
This paper analyses the best batch formations for order picking throughput in narrow-aisle order picking systems. Our analytical comparison finds that a high pick density variation leads to a heavy picker blocking. Simulation experiments show that a distance-based batching algorithm reduces picker blocking by decreasing the number of aisles visited and stabilizing the variation in number of picks per aisle by packing orders tightly, and that the solution quality and mechanism for determining the batch size dictated by the sorting strategy causes varying amounts of blocking. We conclude that combining a distance-based batching method with an appropriate batch sizing strategy will reduce picker blocking and shorten travel in narrow-aisle picking systems.
The Effects of Loosely Coupled Hand-Off Operations on Bucket Brigade Order Picking Systems
Soondo Hong,Youngjoo Kim 대한산업공학회 2018 Industrial Engineeering & Management Systems Vol.17 No.4
Hand-off delays in bucket brigade order picking systems occur when downstream pickers have to wait to receive totes from upstream pickers. This paper introduces a method, termed a loosely coupled hand-off, to reduce waiting delays, and it conducts analytical and simulation studies to identify insights. The loosely coupled hand-off method, which is popular in industry, is preferred by pickers to reduce the expected hand-off delays of downstream pickers. We express the looseness of the hand-off synchronization, i.e., the threshold of the early release, as real number τ ≥ 0. To overcome the throughput reduction, we generalize the looseness from the perspective of a picker’s decision making and throughput improvement and extend the looseness parameter into a practical hand-off framework with measurements including the relative looseness of the hand-off (δ), the increment of work-in-process (WIP) (ω), and the work range of the loosely coupled hand-off (ψ) allowed. We find that the adjusted loosely coupled hand-off framework to balance the hand-off delay reduction and the throughput gains reduces hand-off delay by 30~88% and improves throughput by 2.7~6.4%. In general, to attain the overall system’s throughput improvement, the gains in the hand-off delay require the WIP level and the range adjustments.
Order Batch Formations for Less Picker Blocking in a Narrow-Aisle Picking System
Soondo Hong 대한산업공학회 2015 Industrial Engineeering & Management Systems Vol.14 No.3
This paper analyses the best batch formations for order picking throughput in narrow-aisle order picking systems. Our analytical comparison finds that a high pick density variation leads to a heavy picker blocking. Simulation experiments show that a distance-based batching algorithm reduces picker blocking by decreasing the number of aisles visited and stabilizing the variation in number of picks per aisle by packing orders tightly, and that the solution quality and mechanism for determining the batch size dictated by the sorting strategy causes varying amounts of blocking. We conclude that combining a distance-based batching method with an appropriate batch sizing strategy will reduce picker blocking and shorten travel in narrow-aisle picking systems.
Elsevier 2019 COMPUTERS & INDUSTRIAL ENGINEERING Vol.135 No.-
<P><B>Abstract</B></P> <P>Under a bucket brigade order picking protocol, pickers collaborate to fulfill orders by continuously picking and traveling across pick faces in forward and backward directions. Picker blocking and hand-off delays, however, can significantly affect operational performance. This study investigates flow time (FT), work-in-process (WIP), and throughput (TH) in a two-picker bucket brigade order picking system (OPS) and analyzes the limiting properties of these three performance measures in terms of pick probability, forward walk time, backward walk time, and OPS size, considering both picker and hand-off delays. Numerical analyses and extended simulations confirm that a decrease in the work-in-process level resulting from pickers’ backward walk speeds and hand-offs reduces operational performance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Operational performances of order picking are addressed in closed-form expression. </LI> <LI> The closed-form expressions facilitate numerical analyses of limiting properties. </LI> <LI> Operational performance can drop when the work-in-process level is low. </LI> <LI> A decrease in the work-in-process level results from backward walk and hand-offs. </LI> </UL> </P>